A man and a woman are in a critical condition in hospital after they were hit by a bus in a busy city centre street.
The incident happened at about 2.35pm at the corner of Queen Street and Argyle Street in Glasgow.
The crash, in a busy shopping area, prompted a major response from the emergency services, with a number of fire trucks and a special operations team from the ambulance service involved.
Fire crews used airbags to release the two pedestrians from underneath the double-decker bus.
The two injured people, believed to be aged in their 70s, were taken by ambulance to Glasgow Royal Infirmary where hospital staff describe their condition as critical.
The bus driver was uninjured but was left extremely shaken by the incident.
The collision happened just a few hundred metres from the scene of the bin lorry crash which claimed the lives of six people in December last year.
Police appealed for information about today's collision.
Sergeant Andrew Mair, from the road policing department, said: "Where the crash happened is an extremely busy shopping area and I would appeal to any witnesses who have not yet spoken to police to contact us by calling 101, the non-emergency number for Police Scotland."
First Minister Nicola Sturgeon said on Twitter: "Very concerned to hear about the bus accident in Glasgow city centre. My thoughts are with those involved."
Eyewitnesses told the BBC there had been "horrific" and "hysterical" scenes in the aftermath of the collision.
The Scottish Fire and Rescue Service said it had up to 25 firefighters on the scene.
A spokesman said: "Scottish Fire and Rescue Service crews attended an incident in Queen Street in Glasgow city centre following a call from ambulance control around 2.35pm.
"Four appliances from Calton and Cowcaddens community fire stations attended the incident along with a heavy rescue vehicle from Easterhouse.
"The firefighters, who were working closely with paramedics and doctors, used airbags to release two people from beneath a bus.
"Both casualties were taken to Glasgow Royal Infirmary by ambulance."
Part of the city centre was brought to a standstill as nearby roads were closed and emergency services worked to deal with the situation.
A spokesman for the Scottish Ambulance Service said they had "a number of ambulance crews" on the scene as well as a special operations team and a trauma team.
At the scene, the front half of one bus could be seen partitioned off with a green fabric screen.
A police collision investigation unit was parked nearby and another bus was parked behind the first one. Several traffic officers were present.
A Police Scotland spokeswoman said: "We received a report about 2.30pm that two people had been struck by a bus at the corner of Queen Street and Argyle Street in Glasgow."
A spokeswoman for bus operator First Glasgow said: "We can confirm an incident occurred this afternoon involving a First Glasgow service and two pedestrians.
"We are doing everything we can to support the emergency services and a full investigation to establish exactly what happened is under way."